Steam reverse conveying system of thermal power plant

Abstract

The invention belongs to the technical field of thermal power generation, and discloses a thermal power plant reverse steam supply system which comprises an external heat supply main pipe, the external heat supply main pipe is connected with an external heat supply pipe network, a reverse steam supply pipeline is connected to the external heat supply main pipe, and an auxiliary steam system is connected to the reverse steam supply pipeline through an adjusting valve set. The in-plant feed pump steam turbine is provided with a feed pump steam turbine auxiliary steam electric heater, and a starting drainage heating pipeline is arranged at the tail end of the pipeline close to the feed pump steam turbine. For a newly-built heat supply thermal power plant in which other steam sources exist in a heat supply pipe network outside a plant, the heat supply pipe network outside the plant delivers steam to the power plant to start a generator set instead of fuel gas and fuel oil to start a boiler, so that the cost is reduced, and the carbon emission is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation, and in particular to a steam backflow system of a thermal power plant. Background Art

[0002] Newly built thermal power plants generally require the construction of a gas- or oil-fired starting boiler system to provide steam for generator start-up. Using a starting boiler system for steam supply presents significant initial investment, high fuel consumption costs during operation, pollution emissions from fuel combustion, and the space required for the starting boiler system. Furthermore, during normal generator operation, the starting boiler remains offline for extended periods, requiring maintenance and regular start-up tests. This labor-intensive and expensive maintenance is detrimental to low-carbon emissions reduction.

[0003] Chinese Patent Publication Number: CN107060922B, Publication Date: July 25, 2023, discloses an auxiliary steam system and steam supply method for a thermal power plant. The auxiliary steam system includes a plant-wide auxiliary steam main pipeline and one or more unit auxiliary steam systems. The unit auxiliary steam system includes a unit auxiliary steam main pipeline located on the plant-wide auxiliary steam main pipeline and a low-pressure main steam extraction pipeline located on the unit auxiliary steam main pipeline. The unit auxiliary steam main pipeline is provided with a first valve between the plant-wide auxiliary steam main pipeline and the low-pressure main steam extraction pipeline. The low-pressure main steam extraction pipeline is provided with a second valve and a first drain pipeline located before the second valve. The plant-wide auxiliary steam main pipeline is also provided with a startup boiler steam supply pipeline connected to the startup boiler, and the startup boiler steam supply pipeline is provided with a fourth valve. This system still uses the startup boiler, which has high maintenance costs and is not conducive to low-carbon emission reduction. Summary of the Invention

[0004] The present invention provides a steam reverse delivery system for thermal power plants. For newly built thermal power plants with other steam sources in the off-site heating pipeline network, the system reverses the steam from the off-site heating pipeline network to the power plant to start the generator set, replacing gas or oil to start the boiler, thereby reducing costs and carbon emissions.

[0005] A further object of the present invention is to quickly increase the steam superheat by arranging a feedwater pump electric heater and a start-up drain warming pipe, so as to meet the steam superheat requirement for starting the feedwater pump turbine.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a reverse steam system for a thermal power plant, including an external heating main pipe, the external heating main pipe is connected to the external heating network, the external heating main pipe is connected to a reverse steam pipe, and the reverse steam pipe is connected to an auxiliary steam system through a regulating valve group; the feed water pump turbine in the plant is provided with a feed water pump turbine auxiliary steam electric heater, and a start-up drain heating pipe is provided at the end of the pipeline near the feed water pump turbine.

[0007] Preferably, the auxiliary steam system includes an auxiliary steam main pipe connected to the reverse steam pipeline, which is connected to the auxiliary steam header via an isolation valve. During operation, steam from the external heating network passes through the reverse steam pipeline and the regulating valve group and enters the auxiliary steam main pipe within the power plant. The auxiliary steam system efficiently introduces steam from the external heating network into the power plant, achieving rational distribution and transportation of steam, ensuring a stable steam supply to various auxiliary steam users within the power plant, and improving the operational efficiency and reliability of the entire system.

[0008] Preferably, a regulating valve group is used to adjust and control the flow and pressure of the backflow steam, and a safety valve is installed on the auxiliary steam main pipe on the outlet side of the regulating valve group. This ensures that the safety valve and the downstream auxiliary steam pipeline are not overpressurized. The setting of the regulating valve group can accurately control the flow and pressure of the backflow steam to meet the steam parameter requirements of the power plant. At the same time, the protective effect of the safety valve effectively prevents pipeline overpressure, ensures the safety of system operation, and avoids equipment damage and safety accidents caused by excessive pressure.

[0009] Preferably, there are other heat sources in the off-site heating network that can reverse steam. Before startup, the off-site heating network reverses steam into the power plant, and after startup, the steam is forwarded to the off-site heating network. The reverse steam reaches the auxiliary steam manifold through the auxiliary steam pipe, and the steam is supplied to the auxiliary steam users in each power plant through the auxiliary steam manifold. The startup steam flow is not large, generally 20 to 40 t / h. The superheat of the heating network branch connecting the heating network to the power plant is unstable and often low when the steam flow is small at the beginning. This process design for reverse steam fully utilizes the existing steam resources of the off-site heating network, avoids the use of startup boilers, not only saves fuel costs, but also reduces carbon emissions generated by burning fuel, meeting environmental protection requirements. At the same time, by controlling the flow and pressure of the reverse steam, it can better adapt to the special needs of the power plant startup phase and ensure the smooth startup and operation of the power plant equipment.

[0010] Preferably, the auxiliary steam main pipe is connected to the auxiliary steam electric heater of the feedwater pump turbine through an isolation valve. Since the steam from the external heating network is transported over a long distance and the starting steam flow is small, the superheat is often low, which does not meet the superheat requirements of the starting steam users such as the main steam turbine shaft seal system and the feedwater pump turbine of the power plant. The main steam turbine shaft seal system is generally equipped with an electric heater, so it can be heated by the electric heater to meet the requirements, and there is no need to install an additional electric heater. Heating the steam with an electric heater can effectively increase the superheat of the steam, so that it meets the starting steam superheat requirements of the main steam turbine shaft seal system, feedwater pump turbine and other equipment in the power plant, ensuring the normal startup and operation of these key equipment. At the same time, it avoids equipment failure and unstable operation caused by insufficient steam superheat, thereby improving the reliability of the system.

[0011] Preferably, the feedwater pump turbine auxiliary steam electric heater is used to raise the superheat to no less than 50°C. The feedwater pump turbine of a generator set has high startup steam superheat requirements, generally requiring no less than 50°C. To meet this starting steam superheat requirement, a separate feedwater pump turbine auxiliary steam electric heater is provided to raise the superheat to no less than 50°C, thereby meeting the feedwater pump turbine's startup steam needs. The number of feedwater pump electric heaters provided is one for each unit in the power plant. The auxiliary steam supplying the main steam turbine shaft seal system also has superheat requirements, but power plants generally already have electric heaters for temperature regulation, so a separate electric heater is not necessary. The separate feedwater pump turbine auxiliary steam electric heater can accurately raise the steam superheat to no less than 50°C, ensuring high-quality steam for the feedwater pump turbine during startup, thereby improving its startup efficiency and operational stability. This configuration not only meets the special needs of the equipment, but also avoids startup failure or operation failure caused by insufficient steam superheat, while reducing equipment wear and extending equipment service life.

[0012] Preferably, the auxiliary steam manifold is connected to several user steam pipelines and the feedwater pump turbine steam main, and is used to supply steam for starting and commissioning the feedwater pump turbine. The auxiliary steam required by other steam users in the power plant is supplied through the auxiliary steam manifold. The setting of the auxiliary steam manifold can realize the centralized distribution and supply of steam, and reasonably transport the backflow steam to various users in need of steam in the power plant, including feedwater pump turbines and other auxiliary steam users. This centralized distribution method improves the flexibility and reliability of steam supply, ensures that each user can obtain stable and sufficient steam, optimizes the steam utilization efficiency of the entire power plant, and reduces steam waste.

[0013] Preferably, a power drain heating valve is provided on the startup drain heating pipe. When the superheat of the steam from the external network is low, the feedwater pump turbine auxiliary electric heater is started. At the same time, a startup drain heating pipe and a power drain heating valve are provided at the end of the pipe close to the feedwater pump turbine. The drain heating pipe is strengthened during startup. The feedwater pump turbine auxiliary steam electric heater and the power drain heating valve are operated in combination to increase the steam flow rate, which can quickly increase the superheat of the steam before it reaches the feedwater pump turbine inlet. The provision of the startup drain heating pipe and the power drain heating valve can strengthen the drain heating operation during the startup phase, effectively discharge the condensed water in the pipe, and avoid the condensed water from causing impact and damage to the equipment. At the same time, the operation combined with the feedwater pump turbine auxiliary steam electric heater can quickly increase the steam flow rate and superheat, ensuring that the feedwater pump turbine can obtain steam that meets the requirements at the initial startup, shortening the startup time, improving the startup efficiency, and reducing energy waste and equipment wear caused by startup delays.

[0014] Preferably, the regulating valve group includes an electric isolating valve, a regulating valve, and an isolating valve. The steam in the off-site heating network is fed back into the auxiliary steam system in the power plant through the regulating valve group and used as starting steam for the power plant's generator set. A pressure valve is provided on each pipeline, and the reverse steam passes through the regulating valve group, enters the auxiliary steam main pipe, and is connected to the feedwater pump turbine electric heater and the auxiliary steam manifold. This combination of regulating valve groups can achieve comprehensive control of the reverse steam. The electric isolating valve and the isolating valve can achieve rapid steam cut-off and isolation, ensuring the safety of the system and the flexibility of operation; the regulating valve can accurately adjust the flow and pressure of the steam to meet the needs under different working conditions.

[0015] Beneficial effects of the present invention: The present invention provides a steam reverse delivery system for a thermal power plant. For newly built thermal power plants with other steam sources in the off-site heating pipeline network, the steam is reversed from the off-site heating pipeline network to the power plant to start the boiler instead of gas or oil, thereby reducing costs and carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a schematic flow diagram of a steam backflow system for a thermal power plant.

[0017] Figure markings: 1: external heating main pipe; 2: off-site heating network; 3: reverse steam pipe; 4: regulating valve group; 5: safety valve; 6: auxiliary steam main pipe; 7: feed water pump turbine auxiliary steam electric heater; 8: auxiliary steam manifold; 9: starting drain heating pipe pipeline; 10: power drain heating pipe valve. DETAILED DESCRIPTION

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0019] The installed capacity of thermal power plants accounts for about 46% of my country's installed power generation capacity. In areas with heating demand, power plants supply heat to the outside while generating electricity, which is an efficient and environmentally friendly way of energy production. By generating electricity and heat energy at the same time, improving energy utilization, reducing waste, and helping to reduce carbon emissions, it is an important part of the current global energy transformation. More and more newly built or existing thermal power plants have designed and built heating systems that are connected to external heat networks to supply heat to the outside, with significant benefits. Against the backdrop of the current energy structure adjustment and increasingly stringent environmental protection requirements, energy conservation and emission reduction in thermal power plants are particularly important. Traditional thermal power plant startup methods mostly rely on gas and oil to start boilers, which are not only costly but also generate a large amount of carbon emissions. The thermal power plant startup system of the present invention uses an off-site steam backflow system that innovatively utilizes other steam sources in the off-site heating network 2 to backflow steam into the power plant, providing a new, efficient and environmentally friendly solution for the startup of thermal power plants.

[0020] Inspired by the reverse power flow process before power plant startup, this invention innovatively develops a reverse steam flow system for thermal power plants. This system reverses steam from the external heat network into the power plant, replacing the startup boiler as the starting steam source. By appropriately meeting the startup steam pressure and temperature requirements, the system also meets the generator set startup requirements. This eliminates the need for gas- or oil-fired startup boilers, reduces power plant investment and land occupation, and reduces carbon emissions and other pollutants throughout the plant's lifecycle, contributing to energy conservation and emission reduction.

[0021] Take a large-scale thermal power plant as an example. The area where it is located has a complex and huge heating pipeline network with multiple steam sources in the pipeline network. If fuel oil is used to start the boiler, the fuel consumption cost of the plant during the infrastructure commissioning stage can reach hundreds of thousands of yuan. After it is put into commercial operation, the fuel consumption cost of the unit startup stage can reach hundreds of thousands of yuan each year. At the same time, the large amount of carbon emissions generated by burning fuel oil also puts great pressure on the local environment. With the tightening of environmental protection policies, reducing carbon emissions has become an urgent problem to be solved for the plant. The application of the off-site steam backflow system of the present invention, by utilizing the steam of the off-site heating pipeline network 2, not only significantly reduces the startup cost, but also greatly reduces carbon emissions, achieving a win-win situation of economic and environmental benefits.

[0022] The technical problem addressed by this invention is to address the issues of gas-fired and oil-fired startup boilers in power plants, which often require high investment, limited use, high operating and maintenance costs, and significant carbon emissions and other pollutant discharges. This invention addresses the need for an alternative startup boiler solution. For thermal power plants that utilize other steam sources within their external heating networks, this invention utilizes the plant's internal heating system, the external heating network, and the presence of other steam sources to reversely feed steam from the external heating network into the power plant. This approach has resulted in a startup steam system solution that can replace gas-fired and oil-fired startup boilers.

[0023] like Figure 1As shown in the figure, this system primarily consists of an external heating main pipe 1, a return steam pipe 3, an auxiliary steam system, a feedwater pump turbine auxiliary steam electric heater 7, a startup drain warming pipe 9, and various valves and monitoring devices. The external heating main pipe 1 serves as a key channel connecting the power plant with the external heating network 2, fulfilling the important task of bidirectional steam transportation. The return steam pipe 3 introduces steam from the external heating network 2 into the power plant and connects to the auxiliary steam system via a regulating valve group 4. The auxiliary steam system, comprising an auxiliary steam main pipe 6 and an auxiliary steam header 8, is responsible for distributing steam to various auxiliary steam users within the power plant. The feedwater pump turbine auxiliary steam electric heater 7 is used to increase the steam superheat to meet the stringent startup steam requirements of equipment such as the feedwater pump turbine. The startup drain warming pipe 9 plays a crucial role in draining condensate and increasing steam superheat during the startup phase.

[0024] like Figure 1 As shown, the external heating main pipe 1 is tightly connected to the external heating network 2, forming a vast steam transport network. External heating main pipe 1 is a key component of the entire system. Serving as a "bridge" connecting the power plant and the external heating network 2, it performs the crucial task of bidirectional steam transport. During normal operation, external heating main pipe 1 transports steam generated by the power plant to the external heating network 2, meeting the heating needs of external users. During the power plant startup phase, external heating main pipe 1 is responsible for directing steam from the external heating network 2 into the power plant, providing the necessary steam support for the startup of power plant equipment. This bidirectional transport capability significantly improves steam resource utilization efficiency and ensures flexible operation of the power plant. For thermal power plants with additional steam sources within the external heating network, this system utilizes the internal heating system, the external heating network, and the presence of other steam sources to return steam from the external heating network to the power plant. This creates a startup steam system solution that can replace gas- and oil-fired startup boilers.

[0025] The reverse steam pipeline 3 is a crucial channel for introducing steam from the external heating network 2 into the power plant. Through its connection to the external heating main pipe 1, it precisely transports steam from the external heating network 2 to the auxiliary steam system within the power plant. To ensure the stability and safety of steam transportation, the reverse steam pipeline 3 is equipped with an advanced regulating valve group 4. This regulating valve group 4 comprises a variety of valves, including electric isolation valves, regulating valves, and isolation valves. These valves work together to precisely control the flow and pressure of the reverse steam, ensuring that steam parameters consistently meet the requirements of the power plant equipment during transportation. The safety valve also plays a critical protective role, effectively preventing equipment damage and safety accidents caused by excessive pressure, providing a solid guarantee for the safe operation of the entire system. In actual application at a thermal power plant, the precise control of the regulating valve group 4 ensures that the reverse steam pressure is stably controlled within a specified range, with a fluctuation range of no more than ±0.05 MPa, and a flow regulation accuracy of up to ±0.5 t / h, providing reliable assurance for the stable startup of the power plant.

[0026] The auxiliary steam system is the core hub for the distribution of steam within the power plant. The auxiliary steam main pipe 6 is connected to the backflow steam pipe 3. During operation, the steam from the off-site heating network 2 passes through the backflow steam pipe 3 and the regulating valve group 4 and smoothly enters the auxiliary steam main pipe 6 in the power plant. The auxiliary steam main pipe 6 is connected to the auxiliary steam manifold 8 through an isolation valve. The auxiliary steam manifold 8 is connected to several user steam pipelines and the feedwater pump turbine steam main pipe, distributing the steam evenly to each user in need of steam in the power plant, including the feedwater pump turbine and other auxiliary steam users. In the initial stage of power plant startup, the auxiliary steam manifold 8 can provide a stable steam supply to each user to meet the startup requirements of different equipment. For example, during the startup process of a power plant, the auxiliary steam manifold 8 can simultaneously provide steam to the feedwater pump turbine, the main steam turbine shaft seal system and other auxiliary equipment to ensure that each device works in coordination and successfully completes the startup process.

[0027] After steam from the external heating network is transported over long distances, and when the startup steam flow rate is low, its superheat is often low, making it difficult to meet the needs of startup steam users with strict superheat requirements, such as the power plant's main steam turbine shaft seal system and the feedwater pump turbine. Therefore, this system provides a separate feedwater pump turbine auxiliary steam electric heater 7. This heater is connected via the auxiliary steam main pipe 6 and is used to raise the steam superheat to no less than 50°C. In a certain power plant's generator sets, the feedwater pump turbine has extremely high requirements for the superheat of the startup steam. In the past, insufficient steam superheat often caused equipment failures during startup. The feedwater pump turbine auxiliary steam electric heater 7 of the present invention can accurately raise the steam superheat to a level that meets the requirements, effectively avoiding startup failures and equipment damage caused by insufficient superheat. Each unit in the power plant shares a single feedwater pump turbine auxiliary steam electric heater 7. This configuration not only meets the specific needs of the equipment, but also achieves rational resource utilization and reduces equipment costs.

[0028] When the superheat of the steam from the external network is low, in addition to starting the feedwater pump turbine auxiliary electric heater, a start-up drain heating pipe 9 and a power drain heating pipe valve 10 are set at the end of the pipeline near the feedwater pump turbine. The power drain heating pipe valve 10 on the start-up drain heating pipe 9 can strengthen the drain heating operation during startup and discharge the condensate in the pipeline in time. If the condensate cannot be discharged in time, water hammer will form in the pipeline, causing serious impact and damage to the pipeline and equipment. By working in coordination with the start-up drain heating pipe 9 and the power drain heating pipe valve 10, combined with the feedwater pump turbine auxiliary steam electric heater 7, the superheat of the steam before reaching the feedwater pump turbine inlet can be quickly increased. During the startup process of a certain power plant, when the superheat of the external network steam is low, the startup drain warming pipe line 9 and the power drain warming pipe valve 10 are quickly opened, cooperating with the feedwater pump turbine auxiliary steam electric heater 7 to increase the steam superheat to meet the feedwater pump turbine startup requirements in a short period of time, successfully shortening the startup time by about 15 minutes, improving startup efficiency, and reducing energy waste.

[0029] The starting drain heating pipe 9 is an important and indispensable part of the system during the startup phase. In the initial stage of the power plant startup, due to the small steam flow and low superheat, condensate is easily generated in the pipeline. If these condensate are not discharged in time, it may cause impact and damage to the equipment, affecting the normal startup of the equipment. Therefore, the setting of the starting drain heating pipe 9 is particularly important. By setting a power drain heating pipe valve at the end of the pipeline close to the feed water pump turbine, it can strengthen the drain heating operation during the startup phase and effectively discharge the condensate in the pipeline. At the same time, the starting drain heating pipe 9 also works in conjunction with the feed water pump turbine auxiliary steam electric heater 7 to further optimize the quality of the steam by increasing the steam flow and superheat, ensuring that the feed water pump turbine and other equipment can obtain high-quality steam at the initial startup, thereby shortening the startup time, improving the startup efficiency, and reducing energy waste and equipment wear caused by startup delays.

[0030] The electric isolation valve, regulating valve, isolation valve and safety valve 5 in the regulating valve group 4 cooperate with each other to achieve comprehensive control of the backflow steam. The electric isolation valve and isolation valve can quickly cut off the steam supply in an emergency to ensure the safety of the system. The regulating valve accurately adjusts the flow and pressure of the steam according to the different stages of power plant startup and equipment requirements. The safety valve 5 is installed on the outlet side of the regulating valve group of the auxiliary steam main pipe 6, which can effectively prevent the safety valve 5 and the downstream auxiliary steam pipeline from overpressure. In the event of an abnormal increase in system pressure, the safety valve 5 can be opened in time to release the excessive pressure, avoiding pipeline rupture and equipment damage accidents caused by excessive pressure, and ensuring the stable operation of the entire system. An isolation valve is provided on each pipeline.

[0031] The system is also equipped with a variety of advanced valves and monitoring devices. These are located at key points throughout the system and can monitor steam pressure, temperature, flow rate, and other parameters in real time. They automatically adjust valve openings based on this data to ensure stable system operation. These monitoring devices also feature alarm functions. If an abnormality is detected, they can promptly issue an alert, prompting operators to take appropriate measures, further enhancing system safety and reliability.

[0032] The main features of the present invention are: 1. The power plant's external heating system and startup steam system are coupled, and the innovative concept of backflowing steam from the heat network to the power plant as startup steam is proposed; 2. According to the external heat network steam parameters, the startup steam pressure and temperature requirements are met through appropriate means, including: (1) setting a regulating valve group 4 and a safety valve 5 to control the backflow steam to meet the startup steam pressure requirements to ensure safety; (2) according to the superheat of the backflow steam, for users with superheat requirements, electric heaters are configured, such as feedwater pump turbine electric heaters, and startup drain heating pipes 9 are designed to quickly increase the superheat to meet the startup steam superheat requirements of these users; 3. Based on the above two points, the purpose of eliminating gas or oil startup boilers is achieved.

[0033] The beneficial technical effects of the present invention are mainly reflected in the following aspects: 1. Significant economic benefits For thermal power plants with other steam sources in the external heat network, the off-site steam backflow system of the present invention is adopted to completely eliminate the traditional gas and oil starting boilers, thereby achieving significant cost savings in multiple stages.

[0034] Taking a 2×660MW power plant as an example, after adopting the technical solution of the present invention, the specific benefits are as follows: 1. Infrastructure stage.

[0035] During the power plant's capital construction period, the elimination of the gas or oil-fired boiler system directly saved 2.2 million yuan in initial project investment. Specifically, according to the 2018 design reference cost indicators used during capital construction, the investment cost of a 35t / h oil-fired boiler system was approximately 2.6 million yuan. However, after adopting the system of the present invention, although the investment in a feedwater pump turbine auxiliary steam electric heater 7, a regulating valve group 4, and related pipelines totaling approximately 400,000 yuan was increased, the overall initial project investment was still saved by approximately 2.2 million yuan. This investment savings not only alleviated the financial pressure on the power plant during the capital construction phase, but also provided more abundant financial support for subsequent operations.

[0036] 2. Infrastructure debugging phase.

[0037] During the construction and commissioning of a power plant, the traditional startup method requires the use of a startup boiler, which consumes a lot of fuel. However, the heat network steam startup method of the present invention only consumes heat network steam, saving costs.

[0038] 3. Operation phase.

[0039] During the power plant's long-term operation, the elimination of the boiler startup system saves approximately 100,000 yuan in maintenance costs annually. While this cost may seem small, it accumulates to a significant expense over many years of operation. By adopting the system of this invention, the power plant not only reduces the tedious process of equipment maintenance but also mitigates the potential risks associated with equipment failure, further ensuring stable operation.

[0040] II. Outstanding Environmental and Social Benefits 1. Saving of land resources.

[0041] Traditional gas- or oil-fired boiler systems require a large area of ​​land for the boiler room and related supporting facilities. This invention eliminates the need for a startup boiler, eliminating this land requirement. For modern power plants facing increasingly limited land resources, this land conservation not only reduces construction costs but also provides more space for subsequent plant development and the optimization of the surrounding environment.

[0042] 2. Reduce pollution emissions.

[0043] During operation, traditional startup boilers require the burning of large amounts of fuel oil, which not only produces numerous pollutants such as sulfur dioxide, nitrogen oxides, and particulate matter, but also severely pollutes the surrounding environment. The off-site steam backflow system of the present invention eliminates the need for fuel combustion, directly preventing the emission of these pollutants. This significantly improves air quality around the power plant and reduces negative environmental impacts.

[0044] 3. Reduce carbon emissions.

[0045] Fuel combustion is a significant source of carbon emissions from thermal power plants. By eliminating boiler startup, the system effectively reduces fuel usage, significantly lowering the plant's carbon emissions. Against the backdrop of increasingly severe global climate change, this emission reduction not only helps power plants achieve their low-carbon development goals but also contributes positively to the sustainable development of society as a whole.

[0046] The present invention's external steam backflow system for thermal power plant startup utilizes innovative structural design and scientific operational control, coupling the plant's external heating system with the startup steam system. This system utilizes the plant's external heat network as the startup steam source, replacing the conventional startup boiler within the plant. This system meets the pressure and temperature requirements of various auxiliary steam users. This system successfully replaces gas- and oil-fired startup boilers with steam from the external heating network. In practical applications, the system has demonstrated significant cost savings, reduced carbon emissions, and stable and reliable operation. This system saves space, significant investment, and maintenance costs associated with startup boilers, and reduces pollution emissions from power plants.

[0047] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A steam backflow system for a thermal power plant, characterized in that: It includes an external heating main pipe, which is connected to the external heating network, and a reverse steam pipe is connected to the external heating main pipe, and the reverse steam pipe is connected to the auxiliary steam system through a regulating valve group; The feedwater pump steam turbine in the plant is equipped with a feedwater pump steam turbine auxiliary steam electric heater, and a start-up drain heating pipe is installed at the end of the pipeline close to the feedwater pump steam turbine.

2. A steam backflow system for a thermal power plant according to claim 1, characterized in that: The auxiliary steam system includes an auxiliary steam main pipe connected to the reverse steam pipeline and an auxiliary steam header connected thereto. The auxiliary steam main pipe is connected to the auxiliary steam header via an isolation valve.

3. A steam backflow system for a thermal power plant according to claim 2, characterized in that: The regulating valve group is used to adjust and control the flow and pressure of the reverse steam. The auxiliary steam main pipe is equipped with a safety valve on the outlet side of the regulating valve group.

4. The reverse steam system of a thermal power plant according to claim 2, characterized in that: There are other heat sources in the off-site heating network that can reverse steam. Before startup, the off-site heating network reverses steam into the power plant. After startup, the steam is forwarded to the off-site heating network.

5. A steam backflow system for a thermal power plant according to claim 2 or 3, characterized in that: The auxiliary steam main is connected to the feedwater pump turbine auxiliary steam electric heater through pipelines and isolation valves.

6. The reverse steam system of a thermal power plant according to claim 5, characterized in that: The feedwater pump turbine auxiliary steam electric heater is used to increase the steam superheat to no less than 50℃.

7. The reverse steam system of a thermal power plant according to claim 2, characterized in that: The auxiliary steam header connects several user steam pipelines and the feedwater pump turbine steam main pipe to supply steam for starting and commissioning the feedwater pump turbine.

8. The reverse steam system of a thermal power plant according to claim 2, characterized in that: A power drain heating pipe valve is provided on the start-up drain heating pipe.

9. A steam backflow system for a thermal power plant according to claim 1 or 3, characterized in that: The regulating valve group includes an electric isolation valve, a regulating valve and an isolation valve. The steam in the external heating network is fed back into the auxiliary steam system in the power plant through the regulating valve group and used as starting steam for the power plant's generator sets.

10. The reverse steam system of a thermal power plant according to claim 2, characterized in that: The reverse steam passes through the regulating valve group, enters the auxiliary steam main pipe, and is connected to the feedwater pump turbine electric heater and the auxiliary steam manifold.

Images